ADP3401 Analog Devices, ADP3401 Datasheet - Page 9

• Manufacturer Part Number: ADP3401
• Description: GSM Power Management System
• Manufacturer: Analog Devices

THEORY OF OPERATION
The ADP3401 is a power management chip optimized for use with
the AD20msp425 GSM baseband chipsets in handset applications.
Figure 1 shows a functional block diagram of the ADP3401.
The ADP3401 contains several blocks:
• Four Low Dropout Regulators (Digital, Analog, Crystal
• Reset Generator
• Buffered Precision Reference
• SIM Interface Logic Level Translation (3 V/5 V)
• SIM Voltage Supply
• Power-On/-Off Logic
• Undervoltage Lockout
REV. 0
Oscillator, Real-Time Clock)
CHARGER INPUT
600
500
400
300
200
100
0
10
BACKUP COIN CELL
1 Li-ION OR
TCXO
Figure 14. Output Noise Density
GSM PROCESSOR
REF
3 NiMH
CELLS
VCCA
SIM PIN OF
PROCESSOR
GSM
100
R2
FREQUENCY – Hz
100nF
R1
1k
100nF
10 F
10 F
10k
Figure 15. Typical Application Circuit
2.2 F
FULL LOAD
MLCC CAPS
10
11
12
13
14
1
2
3
4
5
6
7
8
9
VBAT
VCC
PWRONKEY
ANALOGON
PWRONIN
ROWX
CHRON
VRTC
CAP–
SIMBAT
DATAIO
RESETIN
CLKIN
SIMGND
100k
–9–
ADP3401
These functions have traditionally been done as either a discrete
implementation or a custom ASIC design. ADP3401 combines
the benefits of both worlds by providing an integrated standard
product solution where every block is optimized to operate in a
GSM environment while maintaining a cost-competitive solution.
Figure 15 shows the external circuitry associated with the
ADP3401. Only a few support components, mainly decoupling
capacitors, are required.
Input Voltage
The input voltage range for ADP3401 is 3 V to 7 V and optimized
for a single Li-Ion cell or three NiMH/NiCd cells. The ADP3401
uses Analog Devices’ patented package thermal enhancement
technology, which allows 15% improvement in power handling
capability over standard plastic packages. The thermal impedance
(
capacity NiMH cell can be as high as 5.5 V. Power dissipation
should be calculated at maximum ambient temperatures and
battery voltage in order not to exceed the 125 C maximum allow-
able junction temperature. Figure 16 shows the maximum total
LDO output current as a function of ambient temperature and
battery voltage.
However, high battery voltages normally occur only when the
battery is being charged and the handset is not in conversation
mode. In this mode there is a relatively light load on the LDOs.
A fully charged Li-Ion battery is 4.25 V, where the LDOs deliver
the maximum 240 mA up to the max 85 C ambient temperature.
JA
) of the ADP3401 is 60 C/W. The charging voltage for a high
SIMPROG
REFOUT
RESCAP
VTCXO
RESET
SIMON
AGND
DGND
VCCA
CAP+
VSIM
CLK
RST
I/O
28
27
26
25
24
23
22
21
20
19
18
17
16
15
10 F
100
10 F
2.2 F
0.22 F
100nF
CLK TO SIMCARD
I/O TO SIM CARD
RST TO SIMCARD
PROCESSOR
GSM
ADP3401
ANALOG GND
DIGITAL AND
SIM GND